The present invention relates generally to spray nozzles, and more particularly, to air assisted spray nozzles assemblies having particular utility for spraying liquid coolants in metal casting operations.
In metal casting operations, and particularly continuous metal casting systems in which steel slabs, billets, or other metal shapes are extruded from a mold, it is necessary to spray the emerging metal with liquid coolant, namely water, for rapid heat removal. It is desirable that the spray be finely atomized and uniformly directed onto the metal for uniform cooling. Uneven distribution of the liquid coolant results in non-uniform cooling of the metal, which can cause cracking, high stresses, and reduced surface and edge quality. To facilitate liquid particle break down and distribution, it is known to use pressurized air assisted liquid spraying systems. U.S. Pat. No. 5,491,099, assigned to the same assignee as the present application, discloses an air assisted spray nozzle assembly that has been effectively used in continuous casting operations.
In continuous metal casting systems, the cast metal shape commonly is formed in a vertically oriented mold and then withdrawn through a series of closely spaced support rollers where its direction is changed from vertical to horizontal. A plurality of the coolant directing spray nozzles are disposed between each pair of rollers. Due to the large number of spray nozzles that must be employed in such cooling system, a large amount of pressurized air is consumed, which requires costly high capacity air compressors. Heretofore, efforts to reduce air consumption has adversely affected atomization of the coolant liquid and the uniformity of its application on the surface of the cast metal.
The close spacing of the cast metal support rollers creates further problems with such liquid coolant spraying systems. Prior spray nozzle assemblies, such as disclosed in applicant""s above-referenced U.S. Pat. No. 4,591,099, have a nozzle body with an elongated barrel or tube which supports a spray tip between the closely spaced support rollers in close proximity to the moving cast metal such that a flat spray pattern is precisely oriented parallel and between the support rollers. Since the spray tip must be precisely oriented to achieve proper orientation of the flat spray pattern, fixing the elongated spray tip supporting barrel to the nozzle body during manufacture, such as by welding, can be tedious and expensive. Moreover, if a portion of the nozzle assembly is damaged or excessively worn during usage, it is necessary to replace the entire spray nozzle assembly which also can be costly.
It is an object of the present invention to provide a cast metal liquid coolant spray system having air assisted spray nozzles adapted for more efficient and economical usage.
A further object is to provide an air assisted spray nozzle assembly which is operable for producing a discharging flat spray pattern with a high degree of atomization and uniform distribution while requiring substantially reduced air consumption.
A further object is to provide a spray nozzle assembly as characterized above which has a pre-atomizing section designed for more efficient and effective liquid particle breakdown prior to direction through the elongated barrel and downstream spray tip.
Still another object is to provide a spray nozzle assembly of the foregoing type having a pre-atomizing section which minimizes eddy current losses during liquid pre-atomization from converging pressurized air and liquid flow streams.
Yet another object is to provide a spray nozzle assembly of the above kind that is relatively simple in construction and lends itself to economical manufacture and field repair.
A related object is to provide such a spray nozzle assembly in which the elongated spray tip supporting barrel may be easily assembled on the nozzle body while ensuring proper orientation of the spray tip, and hence, proper direction of the discharging flat spray pattern.
Another object is to provide a spray nozzle assembly of such type in which the spray tip support barrel is adapted for easy field repair or replacement.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which: